Complex parts may be manufactured by casting. The casting is a main processing method for metal forming With the progress of market globalization and intense competition and the acceleration of renewal of products, there is an increasing demand for single-piece production and small-scale production of casting parts. Especially, for the sand mold manufacture process of large casting parts, it is required to have a short production cycle and a low manufacture cost. However, most manufacturers in china still adopt conventional wooden mold foundry technique which has a long manufacture cycle, a high production cost and a large consumption of natural resources. In order to solve the problem, a digital processing method and a device of large or medium-size sand mold are proposed.
At present, there are three product modes for casting mold, i.e., conventional sand mold manufacture, rapid forming sand mold manufacture and sand mold processing based on ordinary numerical control machines. For the conventional sand mold manufacture, it is necessary to manufacture a wooden mold according to a casting part, and then perform a sand box foundry to obtain a casting sand mold. The rapid forming sand mold manufacture is applied based on a dispersed-accumulated forming principle, and its basic process includes the steps of: firstly forming a series of layers by delaminating a numerical model of a sand mold in a Z-direction; and then selectively spraying binding agent or perform a laser sintering once one layer of molding sand is paved according to the profile information of layers; and forming three-dimensional sand mold by stacking layer by layer. The sand mold processing based on ordinary numerical control machines uses a numerical machine to numerically cut a sand block according to NC programming and finally obtains a sand mold.
The conventional wooden mold sand mold manufacture is suitable for mass production of casting parts. However, since the wooden mold processing has a long cycle, a high cost, and it is difficult to manufacture a casting mold having a high precision and a good surface quality, it cannot meet the processing requirements of single-piece production and small-scale production. The sand mold manufactured by the rapid forming technique has the following disadvantages. Since the sand mold is processed layer by layer, the processing efficiency is low, which is not suitable for the processing of large casting mold. Sand grains are cohered together by binding agents or laser sintering to form a casting mold having a close-grained inner surface, which has a poor gas permeability such that it is prone to cause defects in casting parts. In addition, since the sand mold is processed layer by layer, step effect would be presented when processing some complex surfaces. The ordinary numerical machine used to perform cutting of sand mold has the following disadvantages. A large amount of waste sand is produced during sand mold cutting processing, which is needed to be cleaned in time. However, the ordinary machine does not include the equipment for cleaning sand. For large casting parts, it is necessary to use a large numerical control processing machine, which increases the cost of equipment. Also, fly sand is produced during the cutting process, precise moving components of the ordinary machine such as guiding rails and leading screws, which are disposed below or near the sand blank being processed, are needed to be protected carefully.